The objective of the National HIV Behavioral Surveillance System (NHBS) is to investigate HIV risk, testing, and prevention services in order to design and evaluate HIV prevention efforts in New York City and throughout the United States. The New York City [unreadable] Department of Health and Mental Hygiene (DOHMH) proposes to conduct an ongoing, cyclical, cross-sectional research study of HIV risk among populations with historically high risk of HIV infection to accomplish this objective. NHBS would include qualitative ethnographic research, quantitative survey research, and HIV testing of three high-risk populations: men who have sex with men (MSM), injection drug users (IDU), and high-risk heterosexuals (HRH). DOHMH proposes to study MSM in the first project year, IDU in the second project year, and HRH in the third project year. The NHBS quantitative survey would include questions in four domains: demographics, HIV risk behaviors, HIV testing, and the use of HIV prevention services. DOHMH will sample members of the target population through venue-based/time-space sampling (MSM cycle) and respondent-driven sampling (IDU and HRH cycles). DOHMH will complete NHBS surveys with a minimum of 500 members of the selected target population each year, for a total of 1500 surveys over the three year project period. DOHMH will conduct HIV testing to estimate HIV prevalence (through Western Blot diagnostic testing) and HIV incidence (through detuned assay STARHS testing) of each target population. Throughout the NHBS research study, DOHMH will collaborate with community partners including the local HIV Prevention Planning Group, HIV Planning Council, and federally-funded community-based organizations. DOHMH will also collaborate with local researchers with knowledge of the target populations and with expertise in qualitative research methods to conduct formative qualitative research on the three target populations to inform and support the main data collection phase. Finally, DOHMH will conduct evaluations of the NHBS system to refine the methods of HIV behavioral surveillance and will conduct descriptive and inferential analyses of NHBS data to describe the target populations and to investigate specific research questions on HIV risk. [unreadable] [unreadable] [unreadable]